br44
Experienced Member
Should a normal healthy 6510 in a C64 breadbin get "freshly brewed coffee" scalding hot, or should it be more like "KFC that's been under a heat lamp all day" warm?
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Just how hot should a 6510 get?
- Thread starter br44
- Start date
Hugo Holden
Veteran Member
It sounds like it needs a temp probe attached (or other method) to get a formal temperature measurement and perhaps compare that with another IC in another machine. IC's in some designs can run "disturbingly hot" and it probably it does shorten their lives. If it is normal for that IC & design and you think it is too hot, you could cool it down somewhat by attaching a heatsink to its body, if there is room for one.
br44
Experienced Member
I don't have another machine, that's why I'm asking. This is the first commodore 64 I've ever tried to restore.
The MPU gets as hot or hotter than the vic 2 in my machine. All the other chips are much cooler. I know the vic 2 is supposed to run hot, and so is the SID, but surely the MPU shouldn't run this hot?
I have reason to suspect the chip is bad. Data line 3 gets really screwy when the MPU gets hot. It starts out okay, and then I watch on the oscilloscope as it goes from 5 volts to 3 volts in a very analog fashion (shrinks down instead of switches down). by then the MPU is too hot to touch for more than a few seconds. It's like sticking your finger in freshly brewed coffee hot.
The dead test results in a dead screen. No reaction. It's as if there's no code running.
When the 6510 is removed from the system, data line 3 never exhibits the same "shrinking" reaction. It goes up to 5 volts like it's supposed to, not the 3v indeterminate state. I've attempted the same test with CIA, SID, and PLA chips removed with no effect. The PLA has already been replaced with an aftermarket solution. All sockets have been replaced with higher quality sockets. All pins on all chips were scrubbed clean of corrosion, and contact cleaner was used.
I tried swapping ram chips around, but the problem does not move. It's always Data Line 3. All other data lines show normal.
br44
Experienced Member
Picture #1 is the baseline. Oscilloscope is set to 1 volt per division, and is probing on data bus 3.
Picture #2 is the same as #1, but now the entire MPU is removed from the board.
Picture #3 same as #1 and #2, the MPU is installed, but pin 34 (data bus 3) is bent up and out of the socket.
br44
Experienced Member
I'm not worried about the power supply. I way over specced it when I removed the original commodore epoxy brick and built something new.
What really sucks is now I have to go find a replacement 6510. The ones on ebay are a LOT of money.
I wonder what caused it to die? Did someone plug in a bad commodore brick before I purchased the computer? Is the 6510 a common failure?
Have you looked into replacement adapters? For example https://tinkerdifferent.com/threads/mos-cpu-replacer-for-c64.996/#post-7982
No idea about them but looking at the prices it might be worth checking it out
Don't think it's common like PLAs or SIDs, but they are old and can die from materials degrading or suboptimal storage conditions
br44
Experienced Member
I saw those, and I saw they were out of stock. However....
Looking at that link a second time made me notice something. It says it's a replacement for the 6510 OR 8500. I just spent the last few minutes googling around, and it turns out the 8500 is a drop in (superior) replacement for the 6510. It's also a little cheaper in places. So... that's good! I like cheaper.
I saw gerber files to build own ones, but haven't checked what parts are needed or available
I thought, before spending money and then it turns out it's something else if there's a way to verify that it's the MPU. You wouldn't know anyone with a C64 to try it out?
br44
Experienced Member
Nope. but then again, where I live I have to drive fifty miles to the nearest major grocery store. So I wouldn't expect anyone to have a C64 around here.
br44
Experienced Member
Update. The 6510 was very dead. Replaced with an 8500, and the computer now functions properly.
robert_sissco
Experienced Member
I just saw this post and was going to suggest an 8500, they are a bit cheaper and tend to run cooler. I would still recommend add heatsinks to the chips as well to help
br44
Experienced Member
Oh yeah, I plan on heatsinking all the warm chips. As of now the computer is still on the workbench due to a bad SID. It'll get heatsinks before getting put back to regular use.
Also, I developed a neat little 3d printed prototype fan adapter for the breadbin. Picture enclosed. The mod makes no permanent changes to the case, and can be removed at any time. It allows a nice gentle (and silent) circulation of air up and out of the top of the case (heat rises). Those are 40mm 5v fans.
